Hydrogenation of rosin compounds



Patented Sept. 12, 1944 UNITED "STATES PATENT orncs HYDROGENATION F nosmCOMPOUNDS Wilbur A. Lazier, New Castle County, Del., 35- signor to E. I.du Pont de Nemours .1: Company, Wilmington, Del., a corporation,Delaware No Drawing. Application March is, 1935, Serial No. 10,194

12 Claims.

.27, 1930, Serial No. 520,473 filed March 5, 1931, Serial No. 584,573filed January 2, 1932, Serial No. 629,754 filed August 20, 1932, SerialNo. 715,- 509 filed March 14, 1934, and serial No, 739,417 filed August11, 1934.

Rosin consists essentially of abietic acid, a derivative of a partiallysaturated alkyl-substituted phenanthrene. 'Abietic acid is known tocontain'one carboxyl group and two olefinic double bonds. Hence, it iscapable of absorbing one hydrogen molecule to form a dihydroabieticacid,

anda second molecule of hydrogen to form the tetrahydroabietic acid inwhich the carbon-tocarbon valences are fully satisfied. There remains,however, an unsaturated carbon-to-oxygen bond in the carboxyl groupwhichmay, ac-

cording toprocedures outlined in this invention,

be replaced with hydrogen in order to transform the carboxyl group to acarbinol group with the formation of tetrahydroabietyl alcohol. If thisreaction is not complete, a portion of the alcohol formed may react withthe remaining tetrahydroabietic acid to form an ester (tetrahydroabietyltetrahydroabietate). A still more exhaustive hydrogenation may convert ahydroabietyl alcohol to a hydroabietane with the complete removal ofoxygen. As might be expected, these various steps in the progressivehydrogenation of abietic acid take place with varying degrees ofdiificulty. Thus, it is much less of a problem to convert abietic acidand its esters into the dihydro derivatives than to force the reactionto the tetrahydro stage. In general, the carboxyl reduction requiresstill more drastic conditions which merge into those required for themost diflicult step of complete removal of oxygen. It is conceivablethat through a proper selection of catalysts the order of these stepsmight be altered so as to produce, for example,an unsaturated rosinalcohol or an unsaturated hydrocarbon. Furthermore, conditions andcatalysts might be selected whereby two or more of the steps in thedirection of the formation of completely hydrogenated material might bebrought about simultaneously.

. Crude rosin and abietic acids are capable of forming anhydrides 5 withcarboxylic acids, and esters with monohydric and polyhydric alcohols,and these anhydrides and esters are subject to the same progressivechanges on catalytic hydrogenation as described above for rosin and theabietic acids themselves.

1 Various attempts have been made heretofore to carry out the partial or.complete reduction of rosin and its derivatives. Applications of thewell known vegetable oil hardening technique, whereinkieselguhr-support'ed copper and nickel catalysts are employed attemperatures in the vicinity of 180 to 225 C. and at pressures below 35atmospheres have resulted in a partial'reduction of the iodine number ofthe resin without affecting the acidic nature of the product through anattack on the carboxyl group. Abietyl alcohol has been obtained,however, through the carboxyl reduction ofabietic acid esters withmetallic sodium as. the reducing agent. In so far as I' am aware, no onehas made advantageous use of highly active chromite catalysts in thehydrogenation of rosin, abietic acid, their esters or their anhydrldestoany reduction products whatsoever prior to my'discovery thereof.Furthermore, no one has heretofore disclosed or succeeded in carryingout a catalytic hydrogenation of a rosin compound in such a manner thatan abietyl orhydroabietyl alcohol or ester is formed. This inventionaccordingly has as an object to carry out the catalytic hydrogenation ofrosin and rosin compounds, particularly esters of abietic acid, by theuse of highly eflicient chromite catalysts. A further object is toprovide an improved process for the production of hydroabi- 40 eticacids and their esters. A still further object is to provide a processfor the hydrogenation of rosin, abietlc acid, hydroabietic acids, theiresters, and their anhydrides to the corresponding abietyl or,hydroabietyl alcohols.

object is to hydrogenate an abietic acid ester to an abietyl alcohol bythe use of a copper chromite catalyst.

These objects are accomplished by bringing a f rosin compound intointimate contact with an excess of hydrogen at a' suitably elevatedtemperature and pressure and in the'presence of a highly active chromitecatalyst. Depending upon the exact composition of the catalyst andtheconditions selected, the hydrogen is absorbed by 5 the rosin compoundwith the formation of one or the pure abietic and hydro-- more of thecompounds of the group comprising dihydroabietic acid, tetrahydroabieticacid, abietyl alcohol, dihydroabietyl alcohol, tetrahydroabietylalcohol, esters of the aforementioned compounds, abietene,dihydroabletene, and abietane. l

The following examples are designed to indicate in greater detail howthe invention may be applied in the production of a number of theproducts named.

Example 1 A highly active nickel chromite catalyst was prepared asfollows: One thousand seven hundred and fifty grams of nickel nitratewas dissolved in three liters of water and mixed with a solution of 750g. of ammonium bichromate in an equal volume of water. The mixedsolution was heated to 90 to 100 C. for 80 minutes with stirring, afterwhich the brick red precipitate formed was washed by decantation anddried. By analysis-the dried product contained 6.7% ammonia and 26.6%nickel and consisted of a complex double chromate of ammonia and nickel.compound was ignited at 400 C. to drive off the ammonia and part of theoxygen and then reduced for 12 hours in a stream of dry hydrogen at 500.C.

Fifteen grams of reduced nickel chromite cata lyst prepared as describedabove was charged into a shaking autoclave together with 100 g. of crudeabietic acid and 200 cc. of ethyl acetate. Hydrogenation was carried outwith rapid agitation at a temperature of 170 C. and under a hydrogenpressure of about 1000 lbs. per sq. in. Hydrogen absorption was rapidduring the first ten minutes and diminished slowly during the course ofseveral hours. The total hydrogen absorption was 1.4 moles per mole ofabietic acid, which conforms to the conversion of the acid to'a mixturecontaining about equal parts of dihydroabietic acid andtetrahydroabietic acid. The hydrogenated product was isolated byfiltering the solution to remove the catalyst and evaporating thesolvent.

Similar results were obtained in a second run in which 95% ethyl alcoholwas used as the solvent and the reaction was carried out at 200 C.

Example 2 iodine number of 96 as compared with 234 for theunhydrogenated material. The acid number was such as to indicate thesubstantial absence of carboxyl reduction under the conditions used.

By way of illustra ng -the advantage of using copper chromite instead ofthe copper catalysts of the prior art, a similar experiment was carriedout in which 186 g. of wood rosin was hydrogenated for 5 hours with g.of a catalyst prepared by precipitating copper carbonate on kieselguhr.The conditions of temperature and pressure were the same as before butthe product This had a Hiibl iodine number of 112.

Example 3 The following procedure indicates a method to be used when thecatalytic hydrogenation is to be I filtered. The resinous products wererecovered developed during precipitation of the copper ammoniumchromate. The precipitate was washed by decantatlon, filtered, anddried, after which it was ignited at a temperature of 400 C. Theresulting copper chromite powder was extracted with 10% acetic acid,washed, and dried.

In an alloy steel tube having a capacity of about 0.4 liter there wasplaced 192 g. of wood rosin and 16 g. of acid-extracted copper chromite:atalyst prepared as described above. The tube was closed, secured in asuitable agitating device and connected with a supply of compressedhydrogen. The tube and contents were agitated rapidly and'heated to'atemperature of 200 C. At a pressure of about 100 lbs. per sq. in.hydrogen absorption took place over a period of about 5 hours. The fusedhydrogenated rosin was filtered and analyzed. By the Hiibl method ofdetermining the unsaturation, the product had an by evaporation of thesolvent and the residue examined by determination of the usualanalytical constants. It was found to have a Hiibl iodine number of,about 50, indicating a substantial clean-up of the carbon-carbon doublebonds. The hydroxyl value of the product was about 138. corresponding toabout a 70% conversion of the rosin ester to the correspondinghydroabietyl alcohol.

Example 4 An autoclave is charged with 200 g. of hydroabietic acid, g.of toluene, and 15 g. of a nickel-chromium oxide catalyst prepared bythe reduction of nickel chromate with hydrogen at a temperature of 500C. for a period of about 4 hours. The rosin mixture is hydrogenated at atemperature of 300 to 350 C. and under a hydrogen pressure of 100 to 300atmospheres. The alcoholic and hydrocarbon derivatives are obtained byevaporation of the solvent. Instead of hydroabietic acid equally goodresults may be obtained in the hydrogenation of ethyl abietate orglyceryl abietate otherwise known as ester gum.

Example 5 The procedure described in Example 1 was applied to ethylabietate in order to convert it into a mixture of ethyl hydroabietates.Two hundred and fifty g. of this material was then charged into anautoclave together with 20 g. of copper chromite catalyst prepared asdescribed in Example 2. The ethyl hydroabietate sample was hydrogenatedfor seven hours with agitation at a temperature of 260 C. and under ahydrogen pressure of about 3000 lbs. per sq. in. Considerable hydrogenwas absorbed. The hydroabietyl alcohol product was recovered by dilutionwith. a solvent followed by filtration and evaporation of the solvent. Adetermination of the saponification number before and after treatmentindicated -a conversion of thecarbethoxy a carbinol group amounting toabout 75%.

Sample 6 Twenty-six grams of barium nitrate and 218 g. of cupric nitratewere dissolved in 0.8 liter of water by heating to 70 C. A solution of128 g. of ammonium blchromate and 0.l liter of 289 6 ammonium hydroxidein 600 cc. of water was added with stirring. The precipitate wasfiltered, dried and ignited at 400 C. The then extracted twice with 10%acetic acid. washed and dried.

Twenty-one grams of copper-barium chromite prepared as described aboveand 212 g. of ethyl abietate were charged into a high-pressureautoclave. Hydrogenation was carried out with agitation at a temperatureof 260 C. and under a hydrogen pressure of 3000 lbs. per sq. iri.-vAbsorption of hydrogen was fairly rapid at iirst and ceased altogetherafter about 5. hours. The

product was cooled, diluted with 200 cc. of ether, and filtered. Afterevaporation of the solvent and the ethyl alcohol formed in the reaction.there remained a water-white viscous mass comprising essentially amixture of hydroabietyl alcohols. The hydroxyl number of this materialapproximated the theoretical value for tetrabydroabietyl alcohol but theHiibl iodine number was about 38, indicating failure of the catalyst tosaturate completely. the olefin bonds.

The hydroabietyl alcohol product described above was subjected to afurther hydrogenation with a nickel catalyst at a temperature of,200f C.

and a pressure of 1800 lbs. per sq. in. This treatment resulted incomplete saturation of the tetrahydroabietyl' alcohol (iodine No. 4)without.- impairing the hydroxyl value. color, or viscomtycharacteristics of the product. ,Carbon, and

hydrogen determinations were in close agreement with "the calculatedvalues for tetrahydrov abietyl alcohol.

Example 7 In a manner similar to that described in Exqample 6, methylabietate was hydrogenated to a mixture of hydroabietyl alcohols by theuse of V the copper-bariumfchromite catalyst. with 200 removed, and thesolvent evaporated oil. Here;

again the color was good and the hydroxyl number indicated that theester had been substanass 100 g. of ester gum was hydrogenated indio'xane with 10 g. of the copper-barium chromite catalyst.Hydrogenation-was somewhat less rapid than-in the case of abietic acidand its esters with monohydric alcohols. Analytical values on the.product,-- however, indicated the same general change in the chemicalcharacteristics of the product.

Another modification of the procedure used in this example consisted ofhydrogenating rosin with the copper-barium chromite catalyst without theaid of a solvent. Under the same conditions-as before, hydrogenabsorption took place at a reduced rate, and the product was more highlycolored than that obtained by use of a solvent..

Al hou h the foregoing examples show in details number of modificationsand variations in procedure that may be practiced in accordance withthe. present invention, it may not'be readily apparent that certainfactors such as temperature, pressure and catalyst composition controlto a large extent the course and rate of the reaction and the nature ofthe products obtained. Among these factors temperature is perhaps themost important. The absorption of hydrogen by the abietic acid nucleusin order to' form-the dihydro derivative takes place inthe temperaturerange 125 to 225 C., depending somewhat-on the catalyst, for the processmay be carried out at the lower end ofthe temperature range with nickelchromite catalyst and at the higher temperatures withcopper the productstherefore consist of one or both of the hydroabietic acids or theiresters. If, however, hydrogenation is carried out at temperatures in theapproximate range of 200 to 400 prominent, depending upon the catalystused,

tially completely converted to the corresponding alcohols. The iodinenumber of the product was about 40.

Example 8 Abietic acid was hydrogenated to a mixture of abietyl alcoholsin. the following manner: The autoclave was charged with 100 g ,--ofabieticacid.

' g. of dioxane, and 10 g. of copper-barlunr chromite catalyst preparedas described in Example 6. At 260 C. and 3000 lbs. pressure,hydrogenation proceeded much the same as in the case of the abietic acidesters. After; hour the product was recovered, filtered and evaporated.The product had an acid value of onb 9 and the hydroxyl valuecorresponded closely to the theoretical value for an abietyl alcohol.

Similar rates of hydrogenation and properties of the product wereobtained by using a good grade of wood rosin in place of the abieticacid.

Alcoh'ol was substituted for the dioxane solvent in one case and provedto be somewhat less satisfactory.

C., then a reduction of the carboxyl group to an alcohol group or -ahydrocarbon group becomes and may proceed simultaneously with orsubsefluently to the conversion of the unsaturated nucleus tothecorresponding saturated nucleus. The preferred temperature range ofthe carboxyl reduction of rosin compounds to hydroabietyl alcoholsis 250to 350 C. when a copper contaming-catalyst isused.

Pressures in excess of atmospheric pressure are to be preferred in anytype of hydrogenation of resin compounds, but here again thecritical-importance of the pressure depends on} the type ofhydrogenationdesired. The carboxyl hydrogenation in particular isfavored by the use of elevated pressures which may range from about 10atmospheres up to the limits of safety of the existing equipment.Ordinarily the pressures used will be in the range of 50 atmospheresto400 atmospheres and seldornin excess Under the conditions described inthis example, II

of 750 atmospheres.

In connection with that part of the invention relating to the nuclearhydrogenation of the abietic acid molecule, the present invention islimited to the use of catalyst compositions comprising highly activechromites of base metals.

However, the invention is much broader in scope as regards catalystsforuse in the higher tem perature range .for the production of anabietyl alcohol. Whereas the critical factors in the hydrogenation ofrosin compounds to abietyl alcohols are the use of high temperatures andpressures, it is necessary that suitable catalysts be selected fromamong a number of different hydrogenating metals and oxides. Mildhydrogenating catalysts such as metallic copper and zinc oxide which arewell known to be suitable for the synthesis of methanol from. carbonmonoxide and hydrogen are in general also suitable catalysts for theproduction of alcohols from abietic acid compounds. On the other hand,there are certain very energetic catalysts such as metallic nickel,cobalt, and iron which are known to catalyze the formation ofhydrocarbons from oxides of carbon and hydrogen. These ferrous metalcatalysts, when employed inthe hydrogenation of abietic acid and itsesters to abietyl alcohols tend to carry the reaction too far with theformation of hydrocarbons. Therefore, if the hydrogenation is to beoperated for the production of alcohols to the substantial exclusion ofhydrocarbons, it is preferable to select as the catalyst a compositioncomprising a member of the group of non-ferrous hydrogenating metalssuch as copper, tin, silver, cadmium, zinc, lead, their oxides andchromites, and oxides of manganese and magnesium. Especially goodresults are obtained with finely divided copper oxide, either wholly orpartially reduced and preferably supported upon an inertsurfaceextending material such as kieselguhr, or promoted by such oxidepromoters as manganese oxide, zinc oxide, barium oxide, magnesium oxide,or chromium oxide. The above-mentioned mildacting catalysts may betermed the alcohol-forming catalysts to distinguish them from the moreenergetic hydrocarbon-forming elements of the platinum and ferrous metalgroups. Elementary nickel, cobalt, and iron when suitably supported onkieselguhr may be used to effect the reduction of rosin compounds withhydrogen, but if the temperature employed is sufficiently high to effecta reduction of thecarboxyl group, the prod uct contains besides alcoholsa preponderance of hydrocarbons, and this disadvantage in most caseswill prove so serious as to preclude the use of these catalysts unlessthe hydrocarbons themselves are the desired end products.

Catalysts suitable for use in the liquid phase batch method ofhydrogenation are preferably prepared in a powder form and may be usedin concentrations ranging from 1% to 15% of the weight of the rosincompound treated. In general, larger concentrations are used for thecarboxyl reduction than for the hydrogenation of the olefin bond. Thepreferred catal st is usually a copper (or nickel) chromite prepared byigniting a double copper (or nickel) ammonium chromate to itsspontaneous decomposition temperature as described in U. S. Patent1,964,000. Many modifications of this procedure have been practicedinvolving the use of acid extraction, hydrogen reduction, and the use ofa supplementary support such as kieselguhr, but these are modificationsin degree only. The essential feature isthe use of copper (or nickel)oxide intimately associated or combined with chromium sesquioxide andthe chromite method of preparation is a convenient method for effectingthe desired association. The method, however, is not limited to copperbut may be practiced in the preparation also of zinc chromite, silverchromite, manganese chromite, etc.

For use in the continuous flow method of hydrogenation which may bepracticed in the case of the more volatile rosin compounds such as theesters with low molecular weight alcohols, certain metal oxidesbelonging to the class of diiilcultly reducible hydrogenatingoxides maybe convenientlyemployed on account of their rugged character and theease with which they may be shaped into hard granules for loading intostationary apparatus. By the term difiicultly reducible is meant thatthe oxides are not substantially reduced to metal by prolonged exposurein a-state of purity to the action of hydrogen at atmospheric pressureand at a temperature of 400 to 450 C. Such oxides which may be suitablefor use as catalysts in the hydrogenation of rosin compounds are zincoxide, barium oxide, manganese oxide, and magnesium oxide. These oxidesmay be employed either alone or in combination with each other or withother metals or oxides which have a promoting action. Preferably thediflicultly reducible hydrogenating oxides also are prepared in the formof chromites, as already indicated in the examples.

Owing to the very low volatility of rosin compounds the preferred methodof hydrogenation involves processing of the material in a liquid state.This may take the formof a normally liquid derivative of abietic acid,or a melt 'of an undiluted resin; or the compound to be hydrogenated maybe dissolved in a suitable solvent. A large number of solvents will befound suitable, including aromatic and naphthenic hydrocarbons, esters,alcohols, ethers, etc. The present invention also contemplates suchmodifications of the process as adaptation to continuous flow over thecatalyst either in the form of a liquid film or diluted vapor of asuitably volatile rosin compound. I

The present invention is applicable to abietic acid, crude or refined,and other acid resins containing unsaturation and/or carboxyl groups.Crude rosin may, for example, be hydrogenated directly. The preferredprocess consists in forming a neutral derivative such as an ester oranhydride by well-known methods and the hydrogenation of said neutralrosin compound. Suitable esters may be prepared from aliphatic,aromatic, or alicyclic monohydroxy compounds such as methyl, ethyl,propyl, butyl, or isobutyl alcohols and cyclohexanol, benzyl alcohol ora phenol. The esters may also be formed by use of a polyhydric alcoholsuch as glycerine or glycol. From the foregoing account, it will beapparent that by the use of chromite catalysts I have effectedsubstantial improvements in the art of preparing hydroabietic acidcompounds. Not only are the new catalysts extremely active in thenecessary hydrogenation reactions, but they are also capable ofwithstanding to a considerable degree such catalyst poisons as oxygenand sulfur. This is presumably because of the potential supply ofunreduced hydrogenating metal which may be continuously activated underthe conditions of hydrogenation. In addition, the present invention hasmade possible a process for producing rosin alcohols and other reductlonproducts cheaply and in unlimited quantities from naturally occurringresins or simple derivatives thereof without the use of expensivechemical reagents.

The hydrogenated rosin products of this invention are useful in a numberof applications where naturally occurring resins such as rosin areless'satisfactory. Hydrogenation of abietic acid to the correspondinghydroabietic acids improves the light stability andmakes the productmore useful than the unhydrogenated materials for use in sizing paperand textiles. Hydroabietic acid esters may be employed as plasticizersand synthetic resin and varnish ingredients. Hydroabietyl alcohols areuseful in the same applications and are particularly valuable componentsof glyptal resins and varnishes containing large proportions ofChina-wood oil.

As many apparently widely difierent embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific embodimentsthereof except as defined in the appended claims.

I claim:

1. The process which comprises catalytically hydrogenating an ester ofabietic acid to the corresponding alcohol at a temperature between 200and 400 C., under a hydrogen pressure in excess 01'10 atmospheres, andin the presence of an alcohol-forming hydrogenation catalyst.

2. The process which comprises catalytically .hydrogenating an ester ofabietic acid to the corresponding alcohol at a temperature between 200and 400 C., under a hydrogen pressure in excess of atmospheres, and inthe presence of a catalyst comprising essentially a chromite of ahydrogenating metal.

3. The process which comprises catalytically' hydrogenating an ester orabietic acid to the corresponding alcohol at a temperature between 200and 400 C., under a hydrogen pressure 'in excess of 10 atmospheres, andin the presence of a hydrogenation catalyst containing copper as anessential constituent.

4. The process which comprises catalytically hydrogenating an ester ofabietic acid to the corresponding alcohol at a temperature between 200and 400 C., under a hydrogen pressure in excess of 10 atmospheres, andin'the presence of a catalyst comprising essentially copper chromite.

5. Process in accordance with claim 1, characterized in that the esterof abietlc acid is ethyl abietate.

6. The process which comprises catalytically hydrogenating ethylabietate at a temperature between 250 and 350 C., under a hydrogenpressure between 50 and 400 atmospheres, and in the presence of a copperchromite catalyst '7. Process in accordance with claim 6, characterizedin that the hydrogenated product obtained is further subjected tohydrogenation in the presence or a nickel catalyst, at a temperature ofabout 200 C., and under a pressure of about 1800 pounds per square inch,thereby completing the hydrogenation of the olefin bond and recoveringthe tetrahydroabietyl alcohol formed.

8. The process which comprises catalytically hydrogenating ahydroabietic compound selected from the class consisting of hydroabieticacid anhydrides and hydroabietic acid esters to the correspondingalcohol at temperature between 250 and 350 C., under a hydrogen pressurebetween 50 and 400 atmospheres, and in the presence or a copper chromitecatalyst.

9. The process which comprises catalytically hydrogenating abietic acidto hydroabietyl alcohol, at a" temperature in excess of 200' C. andunder a pressure in excess of 10 atmospheres, in the presence of nickelchromite.

10. The method of producing a resin alcohol which compriseshydrogenating an alkyl ester or abietic acid by treatment with hydrogenin the presence of a hydrogenation catalyst and under elevatedtemperature and pressure. I

11. The method of producing a resin alcohol which compriseshydrogenating amalkyl ester of abietic acid by treatment with hydrogenin the presence or a hydrogenation catalyst and under a temperatureabove about 200 C. and a pressure of at least 100 atmospheres.

12. The process of producing an alcohol from a rosin compound ottheclass consisting of hydroabietic acid anhydrides and hydroabietic acidesters which comprises the step of catalytically hydrogenating saidcompound to the corresponding alcohol at a temperature between 200 and400 C. under a hydrogen pressure between and 400 atmospheres and in thepresence of an alcohol-forming hydrogenation catalyst.

'W'ILBUR A. LAZIER.

CERTIFICATE OF CORBECTION.

Patent No. 2,358,235. I -September 12, 19M

HILBUR A., mzmn.

It is hereby certified that error appears in the printed. specificationof the above numbered patent requiring correction, aefollowe: Page 5,first column, line 614., for the words "hour houre" reed -tourhoure page5, second column, line 57, for the claim number "12" read --8--; and forthe claims new appearing as "a", "9", "10" and "11" read --9--, --1o--,--11-- and -12-- respectively; and that the said Letters Patent shouldbe read with this correction therein that the me me conform to therecord 'of the case in the Patent Office.

Signed and sealed. this 26th as; or December, A. 1). 191m.

Leslie Frazer (Seal) Acting Commissioner of Patents.

